The present disclosure relates to a semiconductor structure, and particularly to a semiconductor structure including replacement gate devices and an embedded capacitor having a self-aligned metal semiconductor alloy strap, and methods of manufacturing the same.
Deep trench capacitors are used in a variety of semiconductor chips for high areal capacitance and low device leakage. A deep trench capacitor may be employed as a charge storage unit in a dynamic random access memory (DRAM), which may be provided as a stand-alone semiconductor chip, or may be embedded in a system-on-chip (SoC) semiconductor chip. A deep trench capacitor may also be employed in a variety of circuit applications such as a charge pump or a capacitive analog component in a radio-frequency (RF) circuit.
Semiconductor-on-insulator (SOI) devices formed on an SOI substrate or on a hybrid substrate provide high performance in advanced semiconductor chips. In SOI devices, the capacitive coupling between a substrate and semiconductor devices is reduced by the presence of a buried insulator layer. By forming a deep trench capacitor in the SOI substrate, SOI logic devices such as SOI transistors and deep trench capacitors may be formed on the same SOI substrate, thereby enabling embedding of deep trench capacitors into the SOI substrate that also contain high performance SOI logic devices.
Deep trench capacitors are typically electrically connected to an access transistor through a conductive structure, which is referred to as a “strap” or a “conductive strap” in the art. The strap is necessary because electrical current must pass between the access transistor and the inside of the deep trench in order to store electrical charges in the deep trench capacitor or to read the electrical charges stored in the deep trench capacitor. Because a node dielectric in the deep trench is initially formed on the entire inner surfaces of the deep trench, however, prior art methods for forming a deep trench capacitor employ recess etches to remove portions of the node dielectric, followed by the deposition of a conductive material inside the recessed volume to form a buried strap. These processing steps are costly and time consuming, and consequently, embedding of deep trench capacitors increases manufacturing cost and processing time due to the additional processes employed to form the strap.